Chuwong Phongcharoenpanich

TWO-PROBE EXCITED CIRCULAR RING ANTENNA FOR MIMO APPLICATION

This paper presents the analysis and design of a two-probe excited circular ring antenna. The analysis is conducted by using induced emf method and transmission line model. The design process is to choose a suitable radius of the ring for a single probe antenna. Then, the suitable probe length and ring length are determined for the two- probe antenna. Finally, isolation between the two probes is enhanced by insertion of an inductor coil between the probes. The operational characteristics of the prototype antenna at the frequency of 5.2GHz are measured and compared with calculation results. It is evident that these results are in good agreement. The antenna achieved isolation in excess of 20dB and VSWR less than 2 : 1 over the desired bandwidth and a bidirectional radiation pattern with 4dBi gain. This antenna is suitable for Multiple-Input Multiple-Output (MIMO) system covering a long and narrow environment.

Signal-to-interference ratio improvement by using a phased array antenna of switched-beam elements

A phased array antenna of switched-beam elements is proposed to improve the signal-to-interference ratio (SIR). By using 1-bit phase shifters, the main beam of the array is switched to desired signal direction, and with the switched-beam patch antenna elements the null patterns are changeable. The results of radiation patterns show that the interference suppression can be improved. Moreover, the SIR measurement is also set up in multipath environment to ensure the array performance. It is found that the SIR is significantly affected by the multipath environment; however, the SIR improvement of more than 10 dB can be obtained by changing the null patterns.

DETERMINATION OF DIELECTRIC PROPERTY OF CONSTRUCTION MATERIAL PRODUCTS USING A NOVEL RFID SENSOR

This paper presents a concept, by which radio frequency (RF) tags are employed as remotely read dielectric-property sensors to determine qualities of some construction material products (CMPs); e.g., light weight concrete (LWC), mortar specimens and concrete. Using the dependency of the read range of the passive RF identiflcation (RFID) sensor system on the electromagnetic properties of CMPs near or in contact with RFID tags, the qualities of CMPs can be determined through their estimated dielectric properties. Theoretical formulation is provided, and numerical simulations are performed for optimal design of passive RFID tag antennas suitable for RFID sensors and for read-range calculations. In addition, a series of measurements is performed to measure read ranges of the passive RFID sensor system for an LWC as an example of CMPs, and these measured read ranges will be processed appropriately to inversely determine the dielectric constant of the LWC under test, which in turn provides information on its qualities. It is found that the novel RFID sensor can be employed to determine the dielectric properties of the LWC under test with reasonable accuracy.

BIDIRECTIONAL ULTRA-WIDEBAND ANTENNA USING RECTANGULAR RING FED BY STEPPED MONOPOLE

This paper presents an ultra-wideband rectangular ring fed by stepped monopole antenna. The initial parameters of rectangular ring are first considered to obtain the bidirectional pattern with the desired resonant frequency. Subsequently, the parameters of stepped monopole for enhancing impedance bandwidth are investigated. To study the impedance and radiation behaviors, the simulations of the proposed antenna have been carried out. It is found that this antenna offers a bidirectional beam with the impedance bandwidth (return loss lower than −10 dB) covered the frequency range from 3.1 to 10.6 GHz. At the desired direction along this frequency band, the gain of 2.33-5.21 dBi is achieved. Furthermore, the prototype antenna was fabricated and measured to verify the simulated results. Obviously, the simulation and measurement are reasonably in good agreement.

5.8 GHz Notched UWB Bidirectional Elliptical Ring Antenna Excited by Circular Monopole with Curved Slot

This paper presents a UWB bidirectional elliptical ring antenna excited by circular monopole with curved slot for 5.8 GHz band rejection. High Q operation of band notch is obtained in the simulation. The characteristics of the antenna have many attractive features in both technically and economically, such as bidirectional radiation pattern, wide impedance bandwidth, moderate gain, small size, low cost, and easy fabrication. The antenna is desired for application in conventional narrow and long path service area, where some frequency bands pre-occupied by the WLAN standard IEEE 802.11a.

Polarization reconfigurable suspended antenna using RF switches and P-I-N diodes

Polarization reconfigurable square flat antenna using RF switches and P-I-N diodes is presented for WLAN application operated at the center frequency of 2.45 GHz. The proposed antenna consists of the square flat structure, three switches (six P-I-N diodes), transmission-line phase shifters of 0 and 90 degrees. The antenna can be switched between 5 different states: vertical, horizontal and slant polarizations for linear polarization (LP), left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP) by controlling the DC bias of 5 V and the current of 16 mA for the P-I-N diodes. The simulated and measured results show that the proposed antenna can cover the impedance bandwidth from 2.400 GHz to 2.484 GHz and good axial ratio for the circular polarization.

Dual-band RFID-reader antenna using annular plate with curved and rectangular slots

A dual-band antenna for the reader of the Radio Frequency Identification (RFID) applications is proposed. The antenna design to achieve the dual-frequency band is carried out by using the annular plate with curved and rectangular slots. The simulation is done by using CST based on the Finite Integral Method. Furthermore, the parameters of antenna are optimized with the Quasi Newton method. The effects of antenna parameters are analyzed. Along the UHF-RFID band, the pattern is unidirectional beam. The half-power beamwidths in xz- and yz- planes are 78 and 64 degrees, respectively. The bandwidth covers 911–925.6 MHz. The directivity is 8.33 dBi. For 2.45 GHz band, the pattern is also unidirectional beam. The half-power beamwidths in xz- and yz-planes are 58 and 21 degrees, respectively. The bandwidth covers 2.32–2.52 GHz. The gain is 9–10.5 dBi.

Radiation characteristics of a bidirectional antenna using a linear probe in a rectangular ring

This paper reports the radiation characteristics of a low cost and simple structure bidirectional antenna by using a linear probe in a rectangular ring. The radiation pattern is obtained from the Fourier transformation of the aperture field which is derived from the field inside the ring by using Greens function. From the numerical result of the radiated field, for a specific ring dimension, the optimum length which provides the maximum directivity are calculated and chosen as a design parameter. Experimental results, verifying the bidirectional radiation, agree very well with the computational result.

A Switched-Beam Antenna Using Circumferential-Slots on a Concentric Sectoral Cylindrical Cavity Excited by Coupling Slots

This paper presents a switched-beam antenna using circumferential-slot on a concentric sectoral cylindrical cavity excited by coupling slots to operate at 5.8 GHz. The advantages of this antenna are conformal structure, high directivity and capable of switched-beam pattern in six directions. The antenna design starts from a single sector which is capable of switching between radiating and non-radiating modes. The L-shaped coupling slots are proposed to accommodate the switching circuit. Each RF switch is made of two PIN diodes connected in a reverse series connection and placed across the slot at the appropriate location. Subsequently, the exciting probe is designed for matching TM01 mode of the circular waveguide. The measured results of the proposed antenna give a gain of 7 dBi and |S11| less than −20 dB at 5.8 GHz. This antenna is suitable for base station applications that require the switched-beam pattern in the azimuthal plane. Received 22 July 2011, Accepted 25 August 2011, Scheduled 1 September 2011 * Corresponding author: Denchai Worasawate (fengdcw@ku.ac.th). 128 Wounchoum et al.

Short-distance and near-ground signal measurements in a car park of wireless sensor network system at 433 MHz

The short-range and near ground measurements of signal attenuation in the UHF band are performed to study radio wave propagation in a car park for a wireless sensor network application. The measurement setup is based on the radio wave propagation along the row of a parking lot (full of cars) by varying heights of server antenna. In the application, a small antenna and a compact antenna are employed at the server antenna and the sensor antenna respectively, by radiating horizontal polarization. The test points are located under cars and above ground. The transmitter is radiated at 433 MHz with 120 cm, 180 cm and 240 cm of antenna height. The propagation models, such as the two-ray model and the free-space model, are compared with measurement results. These results can be used to approximate the signal level in practical planning of wireless sensor network systems in car parks.